1. Field of the Invention
The present invention relates to a liquid ejection head that ejects liquid droplets from an ejection port and makes the liquid droplets impact on a print medium and a printing apparatus including the liquid ejection head.
2. Description of the Related Art
At present, higher-speed and higher-image quality printing has been demanded for an ink-jet printing apparatus. As means for enabling higher-speed printing in the ink-jet printing apparatus, a reduction in the number of scanning times (number of passes) by a print head and an increase in scanning speed by the print head, etc., can be mentioned.
However, when these means for enabling higher-speed printing are adopted, this is accompanied by an increase in ejection frequency by the print head, so that the flow of air that is generated in a region between the print head and a print medium by ink ejected from the print head is significantly intensified.
As a result, under the influence of an air flow generated by the ink ejected from each ejection port row, ink droplets ejected subsequently are caught up in the air flow, which generates a density unevenness called “wind ripple”. This creates the possibility that the quality of a printed image may not be maintained high. Moreover, in recent years, with the miniaturization of liquid droplets for an improvement in the quality of a printed image, the influence of wind ripple on an image has been further increased.
As methods for solving the above-mentioned problems, there are provided ink-jet printing apparatuses disclosed in U.S. Pat. No. 6,997,538 and U.S. Pat. No. 6,719,398.
U.S. Pat. No. 6,997,538 proposes an ink-jet printing apparatus for which, as shown in FIG. 18, air is blown in a direction orthogonal to a direction in which the ejection port row of a print head extends. Meanwhile, U.S. Pat. No. 6,719,398 discloses an ink-jet printing apparatus for which, as shown in FIG. 19A to FIG. 19C, air is blown in along a direction in which the ejection port row extends. By thus blowing air to the ejection port row, the influence of an air flow to be generated by an ink ejection is suppressed small.
However, for the ink-jet printing apparatus disclosed in U.S. Pat. No. 6,997,538, when a plurality of ejection port rows are formed in a direction orthogonal to a direction in which the ejection port rows extend, it is difficult to uniformly blow air to the respective ejection ports in the print head. An ejection port row located in the vicinity of a gas jet port to blow out air to an ejection port row and an ejection port row located at a position distant from the gas jet port are different in the amount of air reaching thereto. Accordingly, when the amount of air to be blown in is tailored to an ejection port row at a position close to the gas jet port, an ejection port row located at a part distant from the gas jet port can possibly be deficient in air flow. Thus, it is difficult to suppress, for all ejection ports in the print head, the influence of an air flow to be generated by the ink being ejected.
Moreover, in the ink-jet printing apparatus disclosed in U.S. Pat. No. 6,719,398, an ejection port located at a position close to an end portion of a ejection port row close to the gas jet port and an ejection port located at a position close to the center of the ejection port row are likewise different in the amount of air reaching thereto. Also in the ink-jet printing apparatus disclosed in U.S. Pat. No. 6,719,398, it is difficult to uniformly blow in air to all ejection ports in the print head.